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Abstract

Background

'Dry eye' appears to be the main contributor to the symptoms of computer vision syndrome.
Regular breaks and the use of artificial tears or certain eye drops are some of the
options to reduce visual discomfort. A combination of yoga practices have been shown
to reduce visual strain in persons with progressive myopia. The present randomized
controlled trial was planned to evaluate the effect of a combination of yoga practices
on self-rated symptoms of visual discomfort in professional computer users in Bangalore.

Methods

Two hundred and ninety one professional computer users were randomly assigned to two
groups, yoga (YG, n = 146) and wait list control (WL, n = 145). Both groups were assessed
at baseline and after sixty days for self-rated visual discomfort using a standard
questionnaire. During these 60 days the YG group practiced an hour of yoga daily for
five days in a week and the WL group did their usual recreational activities also
for an hour daily for the same duration. At 60 days there were 62 in the YG group
and 55 in the WL group.

Results

While the scores for visual discomfort of both groups were comparable at baseline,
after 60 days there was a significantly decreased score in the YG group, whereas the
WL group showed significantly increased scores.

Conclusion

The results suggest that the yoga practice appeared to reduce visual discomfort, while
the group who had no yoga intervention (WL) showed an increase in discomfort at the
end of sixty days.

Background

Nowadays most people have some contact with computers either at work or at home. This
change has been associated with an increase in complaints of a number of health problems
associated with working at visual display terminals (VDTs) [1]. Eye problems are the single most common complaints [2]. The main visual symptoms which VDT users report are eyestrain, irritation, tired
eyes, a burning sensation, redness, blurred vision, and double vision [2-5]. The symptoms collectively constitute computer vision syndrome [6]. The main contributor to the symptoms of computer vision syndrome appears to be 'dry
eye'.

These symptoms are widely recognized as temporary, however the individual does experience
considerable discomfort [7]. Reducing visual discomfort appears to improve productivity at work [8]. This was indirectly inferred, as adding regular breaks to the work schedule improved
the efficiency between breaks and compensated for the extra time spent in breaks.
Apart from breaks other options which have been tried to reduce discomfort are modifying
the computer location, the lighting and reflection, increasing humidity, the use of
artificial tears [9] or certain eye drops [10].

Yoga is an ancient Indian science which includes the practice of specific postures,
cleansing practices, regulated breathing and meditation [11]. A combination of yoga practices reduced symptoms of visual strain in persons with
progressive myopia [12]. Among software development organizations worldwide, several are in Bangalore city
[13]. Hence the present randomized controlled trial was planned to evaluate the effect
of a combination of yoga practices on self-rated symptoms of visual discomfort in
professional computer users in Bangalore.

Methods

Participants

The participants were 291 persons working in a software company in Bangalore, India.
There was no attempt to calculate the sample size when planning the study. However
based on the effect size obtained in the present study [0.66 with 0.9 power to detect
a significant difference at alpha level 0.05], 50 subjects were required for each
group while in fact at baseline there were 146 subjects in the yoga group and 145
in the control group.

All of them used a computer for at least 6 hours each day, for 5 days in a week. Persons
of both sexes participated in the trial and their ages ranged between 21 and 49 years.
The participants were screened to exclude those who: (i) had consulted a specialist
for their visual symptoms, (ii) had uncorrected errors of refraction, (iii) had clinical
conditions such as Sjögren's syndrome or kerato-conjunctivitis sicca and (iv) used
medication associated with drying of the eyes (e.g., anti-histaminics). None of the
participants had to be excluded based on these criteria. The details of the study
were described to the participants and their consent to participate was obtained.
The project was approved by the ethics committee of the yoga research foundation and
had the approval of the human resource department of the software company.

Design of the study

291 participants were randomized prior to assessment as two groups using a standard
random number table by the researchers responsible. The two groups were then designated
as (i) intervention (i.e., yoga, n = 146) and (ii) wait list control (n = 145) by
an office assistant from the software company who had no other role in the study.
The yoga (YG) and wait list control (WL) groups were comparable with respect to age
(group average (± S.D.) 32.8 (± 8.6) years and 31.9 (± 10.2) years, respectively)
and gender-distribution (11 females in YG group and 13 in WL group).

Both groups were assessed at baseline and after 60 days. During the 60 days the YG
group practiced yoga for an hour per day, for five days in a week. While the YG group
practiced yoga the WL group spent the time in the recreation center of the software
company where 60 percent of them talked to their friends, 12 percent spent time playing
indoor games, 12 percent worked out in the gym and 16 percent watched television.
The WL group had already been spending this time each day doing the same activities
and hence during the 60 day period they were following their usual routine. During
the 60 days there were 84 drop outs from the trial in the YG group and 90 from the
WL group. The large number of drop outs was mainly due to the fact that the participants
had demanding work schedules which interfered with their participating in: (i) the
intervention (YG group) or recreational activities (WL group) and/or (ii) the assessments
(both groups). To be considered as regular in their participation the YG group had
to have a minimum of 38 days of attendance during the 60 day period. The trial profile
is given in Figure 1.

Assessments

Visual discomfort including dryness, irritation, burning, redness, photo-sensitivity
and possible remedial measures (e.g., the use of lubricating eye drops) were determined
using a questionnaire [14]. It had 12 items, each of which had 4 possible choices. These were: (i) absent, (ii)
rarely present (meaning one or two days per week), (iii) often (meaning more than
two days per week) and (iv) continuous. The symptoms were considered during the week
before assessment and the four alternatives (i-iv) were graded as '0', '1', '2' and
'3', respectively. The person who administered the questionnaire and scored the response
sheets was not aware to which group the subjects belonged.

The practice of trataka involves two sets of eye exercises. (i) Shifting the gaze (by moving the eyes alone)
in eight directions. During this exercise, practitioners are asked to use their right
thumb (and when gazing to the left, their left thumb) as a cue to direct their gaze.
The directions are up, down, up to the left, down to the left, up to the right, down
to the right and rotation of the eyes clock-wise and anti clock-wise. (ii) During
the second exercise, practitioners gaze at a flame placed at eye level without blinking.
While gazing at the flame, practitioners are instructed to focus their gaze on the
flame and subsequently defocus while keeping their gaze on the flame. Throughout the
practice practitioners should sit upright and should avoid moving their head to shift
their gaze.

These techniques were selected either because previous research showed that they reduced
physiological arousal [15,16] or based on our unpublished clinical observations.

Data analysis

The data were analyzed using SPSS Version 10.0. Repeated measures analyses of variance
(ANOVA) were carried out with one Between-subjects factor, viz., Groups (with two
levels, i.e., YG and WL groups) and one Within-subjects factor, viz., Assessments
(with two levels, i.e., baseline and day 60). Post-hoc analyses for multiple comparisons between mean values were done with Bonferroni adjustment.

Results

291 participants attended their respective interventions [yoga and control] in three
blocks across 18 months from October 2004 to April 2005.

The repeated measures analyses of variance (ANOVA) showed a significant difference
between YG and WL groups (F = 15.369, DF = 1,115, P < .001). There was no significant
difference between assessments taken at baseline and on day 60. The interaction between
groups and assessments was significant (F = 178.607, DF = 1,115, P < .001), suggesting
that the two factors (groups, assessments) were not independent of each other.

Post-hoc assessments with multiple comparisons of mean values showed a significant decrease
in scores of self-rated visual discomfort for the YG group on day 60 compared to baseline
(P < .001). In contrast, there was a significant increase in scores of self rated
visual discomfort for the WL group on day 60 compared to baseline (P < .001).

The groups mean values with 95% C.I. are given in Table 1. The details of the ANOVA are given in Table 2.

Table 1. Scores of the questionnaire for visual discomfort for yoga and control groups at baseline
[BL] and day 60.

Table 2. Analysis of variance for scores in the 'Dry Eye Questionnaire'

Discussion

In the present single blind, randomized, prospective trial 291 persons working in
a software company were evaluated for self-rated symptoms of visual discomfort. They
were randomized as yoga (YG) and wait list (WL) control groups. Both groups showed
comparable discomfort at baseline. At the end of sixty days the YG group showed decreased
scores, whereas the WL group showed an increase in visual discomfort.

Visual discomfort in professional computer users is contributed to by various factors
such as lighting, glare, display quality, ergonomic positioning of the monitor and
regularity of work breaks [6]. The symptom which largely contributes to subjectively rated visual discomfort is
'dry eye'. Dry eye is itself contributed to by various factors, including certain
diseases (e.g., Sjögren's syndrome, use of certain medication (e.g., anti-histaminics),
gender (being more common in females)), and individual factors [17]. Individual factors include blink rate and completeness of blinking which significantly
affect tear film dynamics and ocular surface health [18,19]. Blink rate especially has been shown to vary with the task performed [20]. The mean (± S.D.) rate of blinking was 22 (± 9) per minute under relaxed conditions,
10 (± 6) per minute while the subjects were reading a book at table level, and 7 (±
7) per minute while working at a video display terminal. Hence the frequency of blinking
reduces while mentally alert and with gaze focused.

Specific yoga practices have been found to bring about physiological changes suggestive
of 'alertful rest' [21]. This description was based on a simultaneous decrease in heart rate and oxygen consumption
along with a reduction in peripheral cutaneous blood flow. Also the visual cleansing
practices used in the present trial have been shown to facilitate visual perceptual
sensitivity in terms of a decrease in optical illusion [22]. A reduction in anxiety has been found to be associated with better visual perceptual
sensitivity [23]. A relaxed state (as described above) is associated with a higher frequency of blinking.
Yoga practice has been associated with better self rated relaxation [24] as well as with physiological relaxation [25]. Hence the reduction in visual discomfort in the yoga group in the present study
may be attributed to an improvement in the ability to focus while remaining relaxed
which may have increased the blink rate.

In contrast to the yoga group the control group showed an increase in self rated visual
discomfort. These differences between the groups could be due to psychological benefits
that are reported with 'additional care' [26]. In the present study the frequent meetings which the yoga group had with the instructor
could serve as additional care and may have contributed to the benefits seen in the
yoga group. The absence of this psychological support and the yoga practice in the
control group may have contributed to increased visual discomfort at follow-up.

A main limitation of the study is that well recognized objective indicators of visual
discomfort (especially dryness) were not measured. It would have been ideal to have
carried out a semi-quantitative estimation of the superficial lipid layer or have
measured the tear breakup time [27]. However another variable which is an objective indicator of VDT related fatigue
was measured in these subjects, and the results were reported elsewhere [28]. This is the critical flicker fusion frequency (CFF), which is the flicker frequency
rate beyond which one can no longer perceive the flicker. Flicker related changes
in the visual system from working at a cathode ray tube (CRT) computer screen have
also been measured [29]. A group of subjects worked for 3 hours at simulated CRT displays with different
flicker rates. The CFF was found to decrease. A similar result was obtained when the
effect of performing the same task on a CRT was compared with the performance on a
back slide projection system (BPS) [30]. The CFF of the group decreased after working on the CRT computer screen while it
did not change when working on the BPS. These studies suggest that the visual system
possibly gets fatigued as a result of viewing supra-threshold flicker.

In the subjects of this study critical flicker fusion frequency was measured using
a standard electronic apparatus [28]. Each subject was assessed in 10 trials (5 each, ascending and descending, given
alternately). The frequency of flicker for the ascending trials was gradually increased
from a minimum of 8 Hz, with 1 Hz increments, till the subjects reported that the
light appeared "fused" or steady. This was the fusion threshold. For descending trials,
the frequency was gradually reduced (1 Hz per step) from 49 Hz, till the subject perceived
the stimulus as "flickering". This was the flickering threshold. The average value
of the ascending and descending trials was used for statistical analysis.

After sixty days the yoga group showed an increase in CFF from a group average (±
SD) of 31.8 (± 2.6) at baseline to an average of 33.6 (± 2.5) after sixty days. In
contrast, the wait list control group showed a decrease in CFF, from a group average
of 32.5 (± 2.5) at baseline to a group average of 31.4 (± 2.5) at the end of sixty
days. Hence the yoga group showed an average increase of 1.8 Hz in the CFF, compared
with an average decrease of 1.1 Hz in the wait list control. This may suggest that
the wait-list control group might have remained prone to visual fatigue, whereas the
yoga group was not.

These results suggest that sixty days of yoga practice may have reduced visual fatigue
based on the self-rated symptoms presented in this study and the CFF findings reported
earlier [28]. However other factors may have influenced the subjective assessment of visual dryness.
For example, certain personality traits were reported to be higher in contact lens
wearers who had dryness of the eyes [31]. This study subjectively evaluated personality traits using the Yatabe Guilford Personality
Test. No personality assessment was carried out in the participants studied here,
which can be considered a limitation of the study. Also, it has been shown that for
yoga practice to be effective participants should be motivated to learn and practice
yoga [32]. Hence it would also have been useful to assess levels of motivation in the yoga
group and correlate them with the reduction in self-rated visual discomfort which
was found.

Conclusion

The results of the present study suggest that a combination of yoga techniques practiced
for 60 days improves self-rated visual discomfort in computer professionals. In contrast,
the wait list control group who continued with their usual routine showed an increase
in self-rated visual discomfort. Hence the practice of yoga can be a potential non-pharmacological
intervention for visual discomfort related to working at visual display terminals
(VDTs).

Competing interests

The principal author and four co-authors declare that they have no competing interests.

Authors' contributions

ST conceived and designed the study and prepared the manuscript. NKV participated
in the conception and design of the study and in compiling the manuscript. MD co-ordinated
the project and supervised the intervention and data collection. RD participated in
the recruitment of subjects, data collection and assisted in statistical analysis.
MNK carried out data extraction and analysis. All authors read and approved the final
manuscript.

Acknowledgements

The research was funded by the Central Council for Research in Yoga and Naturopathy,
Department of AYUSH, Ministry of Health and Family Welfare, Government of India, New
Delhi, India.